1. Technical Field
The present invention relates to an actuator device having a piezoelectric element, a liquid ejecting head and a liquid ejecting apparatus, which are provided with the actuator device and eject liquid droplets from nozzles by the displacement of the piezoelectric element, and a manufacturing method of the liquid ejecting head.
2. Related Art
As a representative example of the liquid ejecting head, an ink jet type recording head which is mounted on an ink jet type recording apparatus can be given. The ink jet type recording head ejects ink from a nozzle which is communicated with a pressure generation chamber, for example, by deforming a vibration plate constituting a portion of the pressure generation chamber by a piezoelectric element, thereby pressurizing ink in the pressure generation chamber. Also, as for such an ink jet type recording head, there are two kinds of the recording head which are put to practical use. One kind uses an actuator device with a longitudinal oscillation mode elongated and contracted the axial direction of the piezoelectric element and one kind uses an actuator device with a flexural oscillation mode.
As the recording head which uses an actuator device with a flexural oscillation mode, there is a recording head having a piezoelectric element which is constituted of a lower electrode film, a piezoelectric body layer formed on the lower electrode film, and an upper electrode film formed on the piezoelectric body layer (for example, JP-A-2006-245247).
Also, such a piezoelectric element is formed, for example, by forming the piezoelectric body layer and the upper electrode film over the entire surface of a substrate in which the lower electrode film is formed, by using film formation technology, and patterning and dividing the piezoelectric body layer and the upper electrode film into a shape corresponding to each pressure generation chamber by using a lithography method.
The actuator device of such a configuration has an advantage that it is possible to arrange the piezoelectric elements with a high density and also a high-speed driving of the piezoelectric element. However, there is a possibility that variation occurs in the displacement characteristic of each piezoelectric element due to variation in the etching end point when patterning the piezoelectric body layer. That is, a portion of the lower electrode film can be also removed when patterning the piezoelectric body layer. However, the removed amount of the lower electrode film is not constant at all portions, and consequently, there is a case where variation occurs in the displacement characteristic of the piezoelectric element. In particular, when the electrode is formed by stacking a plurality of electrically-conductive layers which are different in terms of Young's modulus, if patterning is stopped in the middle of the thickness direction of an electrically-conductive layer having a larger Young's modulus than that of the other electrically-conductive layer, variation in the thickness is apt to influence the driving of the piezoelectric body layer. Further, if the above-mentioned variation exists in a place where is relatively close to the piezoelectric body layer even in a region where the piezoelectric body layer is not formed, it has been found that it influences the driving of the piezoelectric body layer.
Also, such a problem similarly exists in a liquid ejecting head which ejects liquid droplets other than ink, as well as the ink jet type recording head which ejects ink droplets.